Why &mut sqlx::pool::PoolConnection<Postgres> not implemented the trait Executor<'_>

[holicc]

    let mut db: sqlx::pool::PoolConnection<sqlx::Postgres> = ctx.get_db(db_name).await?;

    let a: Vec<A> = sqlx::query_as("select * from account")
        .fetch_all(&mut db)
        .await?;